Optical Transport Network


[OTN Description] [OTN Standards]
[OTN Interface ICs]
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Optical Transport Network Description

Optical Transport Network [OTN]. Three line rates are defined in OTN: OTU1 at 2.666Gbps, OTU2 at 10.709Gbps, and OTU3 defined at 43.018Gbps.
Two constant frame rates are also defined: 20.420kHz [48.971mS]; OTU1, 82.027kHz [12.191mS]; OTU3, and 329.489kHz [3.035mS]; OTU3.
OTN uses Reed-Solomon coding for FEC. The Reed-Solomon codes are 255,239 [239 information symbols, and 16 check symbols]

STM: Synchronous Transport Module [An information structure supporting section layer connections]
... STM-0: 21 E1 lines
... STM-1: 63 E1 lines or 1 E4 line
... STM-4: 252 E1 lines or 4 E4 lines
... STM-16: 1008 E1 lines or 16 E4 lines
... STM-64: 4032 E1 lines or 64 E4 lines
... STM-256: 16128 E1 lines or 256 E4 lines

The structure of the SDH Frame is shown above. The basic SDH frame format is the Synchronous Transport Module [STM], with STM-1 as the base-level.
The SDH frame is formed by 9 rows by 270 bytes with a duration of 125uS.
The first 9 bytes of each row composed of the Section Overhead. The remaining 270 bytes form the Synchronous Transport Module payload.

STS: Synchronous Transport Signal
... STS-1: 28 DS1s or 1 DS3
... STS-3: 84 DS1s or 3 DS3s
... STS-12: 336 DS1s or 12 DS3s
... STS-48: 1344 DS1s or 48 DS3s
... STS-192: 5376 DS1s or 192 DS3s
... STS-768: 21504 DS1s or 768 DS3s

OTN Frame Structure

The structure of the SONET Frame is shown above. The basic SONET frame format is the Synchronous Transport Signal [STS], with STS-1 as the base-level.
The SONET frame is formed by 9 rows by 90 bytes with a duration of 125uS. The first 3 bytes of each row [27 bits] composed of the Transport Overhead [TOH],
the section may also be seen as the Section and Line header overhead.
The remaining 87 bytes form the Synchronous Payload Envelope [SPE]. The overhead bits handle; Section Overhead, Line Overhead, STS Path Overhead, and VT Path Overhead.

Optical Transport Network Standards Information

Optical Transport Network [OTN]; ITU G.709
ITU-T G.709, "Interfaces for the Optical Transport Network", March 2003
ITU-T G.872, "Architecture of Optical Transport Networks", November 2001
ITU-T G.873.1, "Optical Transport Network (OTN): Linear Protection", March 2003

SONET Synchronous Optical NETwork. An ANSI standard [American National Standards Institute, www.ansi.org]
SDH Synchronous Digital Hierarchy. An ITU Standard [International Telecommunication Union, www.itu.int]

Optical Transport Network Interface IC Manufacturers

SPI-3 Description

System Packet Interface Level 3
The Packet Over SONET Physical Layer Level 3 (POS-PHY L3) interface defines the interconnection of Physical Layer devices to Link Layer devices in POS applications.
The interface cores, referred to as SPI-3 cores, perform the interface functions on the Physical Layer or Link Layer side of the interface.
The standard is: System Packet Interface Level 3: OC-48 System Interface for Physical and Link Layer Devices

SPI-4 Description

System Packet Interface Level 4
The Packet Over SONET Physical Layer Level 4 (POS-PHY L4) interface defines the interconnection of Physical Layer devices to Link Layer devices in POS applications.
The interface cores, referred to as SPI-4 cores, perform the interface functions on the Physical Layer or Link Layer side of the interface.
The standard is: System Packet Interface Level 4 (SPI-4) Phase 2 Revision 1: OC-192 System Interface for Physical and Link Layer Devices.

SPI-3 Devices / SPI-4 Devices

Components that operate at the electrical level.

Cortina Systems {Octal OC-48/12/3 Framer / GE MAC, OC-48 ATM SAR / TM with SPI-4.2}

Exar {OC-48 ETHERNET/SONET MULTI-SERVICE FRAMER PROCESSOR}

IDT {SPI-3 to SPI-4 packet-exchange devices}

PMC-Sierra {STS-48c/STM-16-16c ATM & POS Phy with Utopia Level 3, POS-PHY Level 3/SPI-3 & PECL}

Xilinx {FPGA Cores, and Interfaces}

IC Semiconductor Manufacturers

Gigabit Optical Transceiver

Agilent Technologies {10 Gigabit pluggable optical transceivers}

JDS Uniphase Corporation {Transceiver, 10 GbE/FC, XFP, 1310 nm }

Intel {10Gbps XFP Optical Transceiver}

Mitsubishi Electric Corp. {10Gbps Optical Devices, XENPAK Transceiver Module}

NEC Corp. {10Gbps Optical Devices, XENPAK Transceiver Module, SC / LC Interfaces}

OpNext inc.

10G Optical Module Form Factors: [Length x Width]
SFP: 16mm x 42mm
XFP: 23.5mm x 67mm
X2: 42mm x 79mm
XPAK: 42mm x 72mm
XENPAK: 47mm x 118mm
A description of Optical Transceivers is listed on the 10G Optical Module Form Factors page

Definitions:
Data Communications Channel [DCC]
Dense Wave Division Multiplexing [DWDM]
Forward Error Correction [FEC]
Frame Alignment Signal [FAS]
Optical channel Data Unit [ODU]
Optical channel Payload Unit [OPU]
Optical channel Transport Unit [OTU]
Reed-Solomon [RS]

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